Transmissions are used in transportation, agricultural and construction equipment to transmit power from power sources, such as internal combustion engines to equipment for accomplishing a desired task. For example, transmissions are used to properly transmit power to the wheels of a vehicle, or to a vehicle implement. Various industries use gear mechanisms for transmission and conversion of engine power. Various gearbox types such as, for example, gearboxes with constant or variable transmission rates are used. Gearboxes have multiple advantages such as capability of transmission of high torques, low depreciation rate, constant transmission for a selected rotation rate, and high efficiency. However, despite of multiple advantages, the gearboxes have disadvantages such as, for example, limited number of transmission rates, and stepwise (non-linear) transmission rates, which can lower efficiency and cause difficulty in selection of a suitable torque.
Continuously variable transmission (CVT) can be used to overcome the above mentioned disadvantages of gearboxes. A continuously variable transmission (CVT) is a transmission that can change through an infinite number of effective gear ratios between a minimum and a maximum range. In contrast, non-CVT transmissions offer a fixed number of gear ratios. Specifically, hydrostatic CVTs may use a variable displacement pump and a hydraulic motor and transmit power using hydraulic fluid. A swash plate may be used within the variable displacement pump to vary the output of the hydrostatic CVT by adjusting the fluid flowing into the hydraulic motor. Thus, the swash plate may enable the hydrostatic CVT to be continuously variable. Some hydrostatic CVTs may be combined with gear assemblies, drive shafts, and clutches to create a hydro-mechanical CVT. It may be appreciated that in certain applications, such as in construction equipment, a high torque output may be utilized by implements of the construction equipment. Further, a high torque output may be beneficial for low speed movement of vehicles, such as construction vehicles or agricultural vehicles.
In CVTs, transmission rate between an input shaft and an output shaft can be changed continuously in a linear manner such that infinite number of transmission rates is available between predefined lower and upper limits. In a CVT, transmission is provided by friction between parts of the CVT. For example, in a belt driven CVT, friction between a belt and a pulley and in a toroidal CVT, friction between a toroid and disks of the CVT cause the transmission.
However, using the friction mechanism in CVTs cause problems such as limited transmission capability, high depreciation, low efficiency, and lack of stability in the selected revolution. Hence there is a need for a GCVT to produce efficient transmission with continuous/linear variation and high torque output and high power transmission